Sunday, July 5, 2015

Cancer Risk Estimated at Legal OELs and ACGIH Voluntary OELs

I admire Adam Finkel for his intellectual acumen and force.  Adam has been fighting the good fight relative to exposure limits since I have known him.  My friend and colleague Tom Armstrong,  recently made me aware of  items that Adam and his colleagues at the Center for Public Integreity in Washington, DC have published online that provide a remarkably  user-friendly and informative  tool that shows the predicted level of protection provided by OSHA occupational exposure limits (OELs) versus those provided by the American Conference of Governmental Industrial Hygienist (ACGIH). 

One can always argue with how the quantitative level of risks were determined.   Adam and his colleagues anticipated this and provide the details and the rationale online:

For me perhaps the most interesting and useful tool they published in this recent effort  is their “Unequal Risk Investigation” cancer-risk graphic.   A screen shot of this tool is below:

you will be treated to the live version of this tool that allows one to see the difference for OSHA and ACGIH exposure limits for carcinogens on a scale for an estimated 1 in 1000 (10-3) to 1000 in 1000 (10-0)  risk of cancer from exposure at the exposure limits.   You can filter the information by any of 12 categories including construction, manufacturing, health care and agriculture.  The tool also allows you to drill down to the individual chemical for specific risk estimates.  In the above screenshot the details of the estimated risks and uses of trichloroethylene are shown.

For those of you who read this blog regularly, you may recognize that what Adam and his colleagues are doing here is pretty much in line with the idea of Risk@OEL in which the residual risk at any exposure limit is presented as part of the documentation of that limit.  Because of our inability to reasonably establish true thresholds of risk from exposure to non-carcinogens, my thinking is that residual risk should be calculated (with error bands) for all toxic end-points not just cancer.

Indeed, I believe it is important that we all need to be aware of the significant uncertainty that exists around these estimates.   However, uncertainty notwithstanding, my sense is that we need to openly provide these estimates along with our best understanding of the error bands associated with them.

I would love to hear your comments about the information and ideas being presented here.  Do you believe it is OK not to include these estimates and their uncertainties in the documentation of the exposure limits?

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